Requirement

• Durable
• Big enough but not too big that there's no more room for button caption.
• Withstand excessive force

Selection

30mm arcade buttons

• Drawing
• Switches are too big to fit at least 7 of them on a panel.

Cherry MX keyboard switches

• Designed to last, >50 million operations.

• Cheap & multi sourced :
  

  • Official sources:
    • E-switch KS1100OA1AF060
    • Cherry MX1A-11NW
  • AliExpress: you never know what you'll get.  Probably all of these switches will be very noisy.  The advantage is the translucent top of the switch.  It allows to use SMD LEDs, but these should actually be avoided due to excessive stray light.
    • Black (€1.14/10pcs)
    • Brown (€1.12/10pcs)
    • Red (€1.20/10pcs)
    • Blue (€1.17/10pcs)
  • Digikey: only for T-1 3mm LEDs.  Be sure to order LEDs with a height lower than 4.7mm and an LED flange with a diameter of 3.2mm or less:
  • 4 High Efficiency red 3mm through hole LEDs
    • OVLBR4C7 too long
    • WP710A10SEC/J3
    • 151033RS03000 too long and too big
    • XLM2ACR11W
• Requires key caps
  • 104 Keys Transparent ABS Blank Keycaps : €6.43 + €3.71 shipping (might be useful for other projects)
  • 104 Keys Printed variety of options <€10
  • MaxKeyboard & WASD Keyboards offers keys in different colors.  This might be the cheapest if different colors are desired.